UFC champion dethroned by stunning late KO kick (VIDEO)

Leon Edwards was crowned the UFC's welterweight champion in Salt Lake City on Saturday when knocking out pound-for-pound great Kamaru Usman with just 54 seconds to spare in their headline bout at UFC 278.

Edwards was looking to not just become the ruler of the 170lbs division by beating the 'Nigerian Nightmare', but also avenge a 2015 loss to Usman earlier in his career.

Though starting strong in the first round, the Jamaican-born Brit let his foot off the gas and appeared to be on his way to another unanimous decision loss against his foe widely considered to be the best fighter in MMA and making his sixth title defense.

Sat on the stool before the fifth and final round, Edwards seemed to be in his own world looking off into space as his corner screamed at him to "stop feeling sorry" for himself, up the tempo and pull something out of the bag by going on the attack.

As it turned out, however, 'Rocky' was switched on all along. With just 56 seconds to spare, he tricked Usman into defending a left handed punch which then caused Usman to lean to the right.

There to meet him was Edwards' left foot, which immediately knocked Usman out on contact and sent over 18,000 fans in attendance wild.

"Headshot! Dead!" menaced Edwards to the camera, before getting his hand raised by referee Herb Dean.

"It's more for the people that grew up where I grew up," Edwards also said in the octagon when interviewed by Joe Rogan.

"I know it. I felt it. I felt the pressure. I felt the doubt. I felt people saying it couldn't be done.

"I was born with nothing," he added of a rough infancy in Kingston, where he was raised in a one-room "wooden shed" before moving to England aged nine. 

"Look at me now! Look at me now!" Edwards demanded, while also claiming that there is "no pound-for-pound" fighter.

Reflecting on the drama in his post-event press conference, UFC president Dana White, who has confirmed that a rematch to complete their trilogy is next up for both fighters, stated: "That's how crazy the sport is."

"It's what makes this sport the greatest sport in the world. You can sit through four rounds and four minutes and that can happen in a fight. Anything is possible in this sport."

"You think of everything that was on the line for Usman tonight," White went on. "Usman fought with absolute and total confidence the entire night. He fought the perfect fight."

READ MORE: 'I have unfinished business with Masvidal': UFC star Leon Edwards eyes 3-piece & soda revenge 'inside or outside the cage' (VIDEO)

Edwards later conceded that even though he put in "one of my worst performances", "it is what it is". 

"I got a clean finish. ... Even on my worst night, I beat the best pound-for-pound," he bragged.

From Usman, there were no hard feelings either.

"Champs f$ck up sometimes… but we bounce back and come with vengeance!!" he tweeted, later adding: "Damn I love this sport!!! Things happen but… Alhamdulillah we move!!" while also congratulating Edwards and tagging him. 

With White touting Wembley Stadium in England as a potential venue, it now remains to be seen when Edwards - Usman III will take place.